This test measures the amount of an isoenzyme of creatine kinase (CK) in your blood. It is called CK-MB.
Your body makes 3 forms of CK, including CK-MB. CK is found in the heart, muscles, and other organs. These include the small intestine, brain, and uterus. If you have a heart attack, injured heart muscle cells release CK-MB into your blood.
Because many tissues contain CK, high levels of CK can be a sign of a variety of problems. Higher CK-MB may point more directly to heart damage.
Each year millions of Americans go to the emergency room with chest pain, but only a small amount of those people are having a heart attack or other serious, sudden heart problem. This test helps your healthcare provider figure out if you're having a heart attack.
Measuring CK-MB used to be a common tool for diagnosing heart attacks, but healthcare providers use it less often today. Cardiac troponin is now the test of choice for finding a heart attack. This is because cardiac troponin is more specific and more sensitive than CK-MB.
You may need this test if your healthcare provider thinks you are having a heart attack. Symptoms of a heart attack often include:
Pain or discomfort in the chest, such as a squeezing sensation or feeling of fullness
Pain in the neck, back, left arm, or jaw
Shortness of breath
Lightheadedness or dizziness
Nausea or vomiting
Your healthcare provider may also order a test to measure cardiac troponin (CTn). This test is more often used than CK-MB because it more specifically shows heart damage.
Your healthcare provider may also order an electrocardiogram (ECG). This is done to measure electrical activity in your heart and help diagnose a heart attack.
Test results may vary depending on your age, sex, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
Levels of CK-MB do not rise in your blood within the first 4 to 6 hours after a heart attack. You may need to have repeated tests to see if you've had a heart attack.
Higher levels of CK-MB may mean that you have had a heart attack or have other heart problems. These include:
Myocarditis. This is an infection and inflammation of the heart muscle.
Pericarditis. This an infection and inflammation of the thin sac that surrounds the heart.
Higher levels of CK-MB may also mean more of the heart was damaged in the attack.
Higher levels may also be caused by muscle damage elsewhere in your body, by diseases that affect your muscles, and by trauma to your chest.
The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.
Having a blood test with a needle has some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.
Timing is important. If you have the test too soon after a heart attack, you may have a false-negative result.
Strenuous exercise and cocaine use can also affect your results.
You don't need to prepare for this test. Tell your healthcare provider about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.